Tumble dryers normally operate such that wet laundry which is contained in a rotatable drum in the interior of the tumble dryer, is dried by a hot air stream. The hot air stream is conducted from an air supply means through the flow passage, which normally extends between the drum and a rear wall of the tumble dryer, into the drum and through the wet laundry. The flow passage has installed therein a heating assembly, which heats the hot air stream by means of at least one heating element. When the tumble dryer is in operation, at least one temperature sensor detects the temperature of the hot air stream. If a predetermined limit temperature is exceeded, the heating element will be switched off by the control unit of the tumble dryer. A temperature control of this type allows the laundry to be dried at a temperature, which is suitable for textiles. In addition, said temperature control is executed for preventing the rear wall of the tumble dryer to be heated to inadmissibly high temperatures which would endanger the operating safety of the tumble dryer.
DE-A-33 40 313 describes a tumble dryer in which a panel heater is arranged in a flow passage. In the panel heater of DE-A-33 40 313, two heating elements and two temperature sensors are located.
In said known heating assemblies, temperature measurement is, however, not precise so that the heating elements may be excessively heated, whereby the maximum admissible temperature for gentle drying may be exceeded and the outer wall of the tumble dryer may be heated to inadmissible temperatures.